Recently, as touch screens that can replace independent input devices, such as a keyboard and a mouse, by converting positions directly contacting a person's hand or an object into electrical signals, on the front face of image display devices are increasingly used, possible uses of stylus pens for the touch screen panels are rapidly increasing. A stylus pen is usually designed to be thin relative to a person's hands, and particularly, the tip portion for touch input is designed to be thin, such that it is useful to perform precise input to the touch panel. However, there is a limit to the extent to which it is possible to make the tip portion of the stylus pen thin and still be useful, particularly in a stylus pen used for a capacitive type touch panel. A sufficient area of the tip portion is required to provide capacitance change for the capacitive type touch panel so that the capacitance touch panel is able to sense touch input. Therefore, a stylus pen to provide touch input to a capacitive type touch panel has a relatively large area at the tip portion, such that the stylus pen covers the portion where touch input is applied to the screen. Such a configuration is sometimes inconvenient.
Coordinates of the small conductive ball tip of certain embodiments of the stylus as registered by a capacitive touch screen (CTS) may not be exact. For example, if one slowly draws a diagonal line on the CTS, the line may produce small back and forth lines that may appear to be “Wiggles.” The amplitude of the Wiggles may vary from one CTS to the next. The coordinate registration error may be due to the CTS having a fairly widely spaced drive and sense electrodes. For example, the Apple® iPad™ CTS has electrodes spaced approximately 4 millimeters (mm). In some situations, the CTS may be designed to register a finger pushed flat against the screen. Thus in those situations, such a large area will span perhaps 5 to 10 mm. The centroid finding algorithm of the CTS's interface integrated circuits works may then prefer that large area of significant coupling capacitance. When the CTS only detects the small electrostatic footprint of, for example, a ⅛ inches (″) diameter metal ball, as may be used in certain types of a stylus, the centroid finding algorithm may provide inexact coordinates.
Further, a tip or tip portion for a stylus may include a smooth conductive ball at the end of a rod constructed in conductive material such as metal or conductive polymer. The rod may connect the conductive ball to an input stage of the stylus. Various lengths of the supporting rod could be used on various embodiments. A longer supporting rod may increase the “skew” experienced when using the stylus. In some situations, the stylus may be held at a usual writing or drawing angle. This may result in the coordinates that are registered by the touch screen being “pulled” away from a location directly below the ball tip, towards the body of the stylus. This may occur due to the addition of the desired sensing and driving of the electrodes of the CTS by the tip ball, the supporting rod may be seen, in an electrostatic sense, by the CTS electrodes.